//
//  ViewController.m
//  ceshiQURGB
//
//  Created by 恩叔 on 16/4/24.
//  Copyright © 2016年 enshu. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()
@property (nonatomic, strong)UIImageView *img;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.img = [[UIImageView alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];
    _img.image = [UIImage imageNamed:@"1"];
    [self.view addSubview:_img];
    CGPoint point = _img.center;
    [self getPixelColorAtLocation:point];
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

/*
 CGContextRef CGBitmapContextCreate （
 　　void *data，
 　　size_t width，
 　　size_t height，
 　　size_t bitsPerComponent，
 　　size_t bytesPerRow，
 　　CGColorSpaceRef colorspace，
 　　CGBitmapInfo bitmapInfo
 　　）;
 
     参数data指向绘图操作被渲染的内存区域，这个内存区域大小应该为（bytesPerRow*height）个字节。如果对绘制操作被渲染的内存区域并无特别的要求，那么可以传递NULL给参数date。
 　　 参数width代表被渲染内存区域的宽度。
 　　 参数height代表被渲染内存区域的高度。
 　　 参数bitsPerComponent被渲染内存区域中组件在屏幕每个像素点上需要使用的bits位，举例来说，如果使用32-bit像素和RGB颜色格式，那么RGBA颜色格式中每个组件在屏幕每个像素点上需要使用的bits位就为32/4=8。
 　　 参数bytesPerRow代表被渲染内存区域中每行所使用的bytes位数。
 　　 参数colorspace用于被渲染内存区域的“位图上下文”。
 　　 参数bitmapInfo指定被渲染内存区域的“视图”是否包含一个alpha（透视）通道以及每个像素相应的位置，除此之外还可以指定组件式是浮点值还是整数值。

*/
///获取图片中单个点的颜色
- (UIColor*) getPixelColorAtLocation:(CGPoint)point {
    UIColor* color = nil;
    CGImageRef inImage = self.img.image.CGImage;
    // Create off screen bitmap context to draw the image into. Format ARGB is 4 bytes for each pixel: Alpa, Red, Green, Blue
    CGContextRef cgctx = [self createARGBBitmapContextFromImage:inImage];
    if (cgctx == NULL) { return nil;  }
    
    size_t w = CGImageGetWidth(inImage);
    size_t h = CGImageGetHeight(inImage);
    CGRect rect = {{0,0},{w,h}};
    
    // Draw the image to the bitmap context. Once we draw, the memory
    // allocated for the context for rendering will then contain the
    // raw image data in the specified color space.
    CGContextDrawImage(cgctx, rect, inImage);
    
    // Now we can get a pointer to the image data associated with the bitmap
    // context.
    unsigned char* data = CGBitmapContextGetData (cgctx);
    if (data != NULL) {
        //offset locates the pixel in the data from x,y.
        //4 for 4 bytes of data per pixel, w is width of one row of data.
        @try {
            int offset = 4*((w*round(point.y))+round(point.x));
            NSLog(@"offset: %d", offset);
            int alpha =  data[offset];
            int red = data[offset+1];
            int green = data[offset+2];
            int blue = data[offset+3];
            NSLog(@"offset: %i colors: RGB A %i %i %i  %i",offset,red,green,blue,alpha);
            color = [UIColor colorWithRed:(red/255.0f) green:(green/255.0f) blue:(blue/255.0f) alpha:(alpha/255.0f)];
        }
        @catch (NSException * e) {
            NSLog(@"%@",[e reason]);
        }
        @finally {
        }
        
    }
    // When finished, release the context
    CGContextRelease(cgctx);
    // Free image data memory for the context
    if (data) { free(data); }
    
    return color;
}
///创建取点图片工作域：
- (CGContextRef) createARGBBitmapContextFromImage:(CGImageRef) inImage {
    
    CGContextRef    context = NULL;
    CGColorSpaceRef colorSpace;
    void *          bitmapData;
    int             bitmapByteCount;
    int             bitmapBytesPerRow;
    
    // Get image width, height. We'll use the entire image.
    size_t pixelsWide = CGImageGetWidth(inImage);
    size_t pixelsHigh = CGImageGetHeight(inImage);
    
    // Declare the number of bytes per row. Each pixel in the bitmap in this
    // example is represented by 4 bytes; 8 bits each of red, green, blue, and
    // alpha.
    bitmapBytesPerRow   = (pixelsWide * 4);
    bitmapByteCount     = (bitmapBytesPerRow * pixelsHigh);
    
    // Use the generic RGB color space.
    colorSpace = CGColorSpaceCreateDeviceRGB();
    
    if (colorSpace == NULL)
    {
        fprintf(stderr, "Error allocating color spacen");
        return NULL;
    }
    
    // Allocate memory for image data. This is the destination in memory
    // where any drawing to the bitmap context will be rendered.
    bitmapData = malloc( bitmapByteCount );
    if (bitmapData == NULL)
    {
        fprintf (stderr, "Memory not allocated!");
        CGColorSpaceRelease( colorSpace );
        return NULL;
    }
    
    // Create the bitmap context. We want pre-multiplied ARGB, 8-bits
    // per component. Regardless of what the source image format is
    // (CMYK, Grayscale, and so on) it will be converted over to the format
    // specified here by CGBitmapContextCreate.
    context = CGBitmapContextCreate (bitmapData,
                                     pixelsWide,
                                     pixelsHigh,
                                     8,      // bits per component
                                     bitmapBytesPerRow,
                                     colorSpace,
                                     kCGImageAlphaPremultipliedFirst);
    if (context == NULL)
    {
        free (bitmapData);
        fprintf (stderr, "Context not created!");
    }
    // Make sure and release colorspace before returning
    CGColorSpaceRelease( colorSpace );
    
    return context;
}
@end
